My college says I obtained course materials I should have had access to. What sanctions can they hit me with?

Being accused of having unauthorized course materials is serious. The question would be, were you, in fact, in the wrong? Did the professor actually provide clear instructions as to what you were supposed to be able to have or use say if it's for a given assignment or exam, or did the professor even say, change the instructions at some point in the process where you would not be culpable for what you're being accused of?

If you did, in fact, have unauthorized course materials, it would depend on what you did with them in terms of if you gained an academic advantage. If so, to what degree and what other say, circumstances were involved at various stages of the school, say an undergraduate student would be held to a high standard that is even more so the case for a student at the master's level or a PhD student or a law student, or a medical student, for example.

It can vary in terms of what the potential outcomes can be both on the particular students at hand, in terms of their level of schooling, the circumstances involving the case, and other factors. It can result in anything from say, probation, suspension, expulsion, possibly a warning. Having an experienced attorney-advisor in your corner will help you best understand and navigate the process and they should be involved as early as possible in the case.